The Thai Ministry of Public Health strives to provide the HIV infected people of Thailand with affordable antiretrovirals (ARVs). A fixed-dose combination tablet of 3TC, NVP, and d4T is recommended as first-line treatment in HIV infected adults in Thailand. There has been no similar product developed for children for several reasons: pediatric dosing is based on age, weight, or body surface area; developmental changes may influence the bioavailability and pharmacokinetics (PK) of ARVs; and medication adherence may also be a problem. The purpose of this study is to gather bioavailability and PK data in children taking a fixed-dose tablet of 3TC, NVP, and d4T. This information will then be compared to the bioavailability and PK of the individual liquid formulations of these ARVs.